Webb's auction house is standing by the restoration treatment of a valuable Colin McCahon painting it withdrew from sale 10 days ago.
The company pulled the work from auction less than three hours before it was due to go under the hammer.
Webb's initially refused to give an interview about the work, a 1959 enamel on board painting called Elias that had been held in the collection of artist Doris Lusk until her death.
Photographs showed significant retouching, most noticeably the covering up of patches of a dark under-surface that had been showing through a deteriorated strip of pale yellow paint.
Fairfax understands another auction house had declined to handle the sale of the work, believing too much conservation work was required.
On Friday, Sophie Coupland, head of Webb's fine art department, said the painting's condition had been taken into account when a price estimate of $250,000-$300,000 had been set. (Two years ago, another work from the Elias series fetched half a million dollars).
"We knew it had condition issues, there was no two ways about that," said Coupland. ''Anyone can see that and a big part of the conversation about how to price the work was around condition.''
She revealed the main conservation work had been carried out on the instruction of the seller.
"That all occurred prior to us ever seeing it."
She said its stability had been confirmed by Auckland conservator Birgit Lulek, who had carried out a smaller amount of additional treatment.
Coupland said the decision to not respond to questions last week was ''absolutely just a lack of judgment".
"I suppose we just kind of panicked," she added. "In actual fact, we didn't see there was a story in it''.
According to Coupland, Webb's was in discussion with ''a couple of people'' who were interested in buying the work.